In known tire curing presses, an upper mold part is movably guided in vertical direction with respect to a lower mold part by means of long-stroke cylinders to allow opening and closing of the mold cavity. To provide mold parts in close contact during vulcanization of a tire, the upper mold part is locked in its closed position when being placed on the lower mold part. The mold pressure applied on the mold parts during vulcanization is provided by suitable pressing cylinders.
Practice has shown that in tire curing presses of this kind problems have been encountered to guide the upper mold part in an accurate manner so that mismatches of the two parts of the mold occurred, especially when the upper mold part is attached to a wide tie-bar. During starting of the press, considerable temperature drops are obtained between those areas subjected to heat and the cold parts so that respective tolerances play or clearance must be provided in dimensioning the guides in order to avoid jamming.
From the German Pat. No. 2 358 702 a system of tire curing presses is known in which the upper mold part is connected to a headpiece via lock cylinder devices and is guided along lateral plate-shaped portions of the press. This guidance necessitates a considerable tolerance because of the temperature rise which is to be expected during operation of the press in view of the wide distance of the guide surfaces. Moreover, the upper mold part supported in this manner performs transverse movements and thus becomes misaligned with the lower mold part. This results in inaccuracies during closing of the press and vulcanization of the tire.